Heat pipes remove heat from the source in a two-phase process. As heat is generated, a
liquid at one end of the pipe evaporates and releases the heat to a heat sink by
condensation at the other end. The liquid is returned to start the process over through a
wick structure on the inside of the heat pipe.

The Heat Pipe - How it works

Thermacore's Heat Pipe technology provides a cost effective solution for laptop cooling
applications or for any other electronic cooling where minimal space and low maintenance
requirements are involved.

Heat pipes are relatively simple devices. They passively transfer heat from the heat
source to a heat sink where the heat is dissipated. The heat pipe itself is a vacuum-tight
vessel that is evacuated and partially filled with a minute amount of water or other
working fluid. As heat is directed into the device, the fluid is vaporized creating a
pressure gradient in the pipe. This forces the vapor to flow along the pipe to the cooler
section where it condenses, giving up its latent heat of vaporization. The working fluid
is then returned to the evaporator by capillary forces developed in the heat pipe's porous
wick structure, or by gravity. (See illustration)

The Thermacore Laptop Heat Pipe Solution

Thermacore has taken heat pipe technology originally used for space applications and
applied it to laptop computer cooling. It is an ideal, cost effective solution. Its light
weight (generally less than 40 grams), small, compact profile, and its passive operation,
allow it to meet the demanding requirements of laptops.

Thermacore's HS-NB series of heat pipes is specifically designed for P-5 notebooks, but
can also be adapted for other processors and component cooling. For an 8 watt CPU with an
environmental temperature no greater than 40°C it provides a 6.25°C/watt thermal
resistance, allowing the processor to run at full speed under any environmental condition
by keeping the case temperature at 90°C or less.

One end of the heat pipe is attached to the processor with a thin, clip-on mounting
plate. The other is attached to the heat sink, in this case, a specially designed keyboard
RF shield. This approach uses existing parts to minimize weight and complexity. The heat
pipe could also be attached to other physical components suitable as a heat sink to
dissipate heat. (See photo of inside of laptop computer)

Thermacore's heat pipes provide a small profile without any interference to existing
components and can be easily adapted to an existing package design. Because there are no
moving parts, there is no maintenance and nothing to break. Some are concerned about the
possibility of the fluid leaking from the heat pipe into the electronics. The amount of
fluid in a heat pipe of this diameter is less than 1cc. In a properly designed heat pipe,
the water is totally contained within the capillary wick structure and is at less than 1
atmosphere of pressure. If the integrity of the heat pipe vessel were ever compromised,
air would leak into the heat pipe instead of the water leaking out. Then the fluid would
slowly vaporize as it reaches its atmospheric boiling point. A heat pipe's MTTF is
estimated to be over 100,000 hours of use.

The Cost Effectiveness of Heat Pipes

The flexibility of the Thermacore heat pipe solution provides an effective method for
cooling processors in laptops. The cost of heat pipes designed for laptop use is very
competitive compared to other alternatives. Cost is partially offset and justified by
improved system reliability and the increased life of cooler running electronics. Heat
pipes, in quantity, cost a few dollars each while an entire cooling system will cost
between $5 - $10 in production quantities, depending on the final design. Standard design
products are available to reduce cost even further.

The Swales Heat PipeOur heat pipes improve performance
and extend equipment life, while they dissipate heat. The pipe can be made of flexible
material or in a variety of shapes and sizes. This allows it to accommodate design
constraints, yet still efficiently transport unwanted heat to an available heat sink.

The Swales heat pipe features: High thermal conductivity Lightweight compact construction Temperature uniformity No need for external power Reliable, no-maintenance design Silent, vibration free operation Quick thermal response Ability to operate in extreme
environments Variety of shapes and sizes Allows heat sink to be located away
from heat source
How a Heat Pipe Works
A heat pipe is a passive device that transports heat efficiently from one point to
another. It is made of a sealed container with a working fluid and wick, or grooves,
inside. As heat is applied to the evaporator section, the working fluid vaporizes and
flows to the cool or condenser section of the heat pipe. There the working fluid
condenses, releasing the heat of vaporization.

Swales can design and manufacture heat pipes in the size, shape and power rating you
require. Our applications engineers are experienced, knowledgeable and available to assist
you in optimizing a heat pipe system that will satisfy your needs.